Many seeds require changes in light levels to start their internal germination chemical processes. This frequently happens when soil is moved around or over shadowing plants die back during cold periods or even fires – or for example are exposed by being washed down a river and landing on a bright sunlit river bank with seasonal storms.
Altering your light levels can imitate the changes in the seasons out in the open ground that trigger the seed to start their internal chemical clock and initiate the growing. This is usually in combination with moisture and exposure to oxygen.
However there are some seeds that prefer to be sown and covered in soil or compost to enhance their germination process – effectively being in the dark allows them to germinate more effectively.
But there are many seeds that don’t really care about light and mainly respond just to moisture and heat levels changing and will germinate in light or in darkness.
You can often improve your germination results by looking at the environment that these plants have evolved and would normally be growing and would normally be found in the wild.
Here are some that have been collated from online and published reference material.
| Seeds that need light | Seeds that need dark | Seeds that don’t really care |
| Vegetables & herbs | ||
| Feverfew | Calendula | Broccoli |
| Salvia | Coriander | Cabbage |
| Lettuce | Parsley | Cauliflower |
| Celery | Fennel | Cucumber |
| Dill | Eggplant | |
| Savory | MuskMelon | |
| Pepper | ||
| Squash | ||
| Tomato | ||
| WaterMelon | ||
| Flowers | ||
| Begonia | Cornflower | Alyssum |
| Impatiens | Delphinium | Aster |
| Petunia | Forget me not | Balsam |
| Primula | Gazania | Celoisa |
| Coleus | Pansy | Cosmos |
| Strawflower | Schizanthus | Dahlia |
| Campanula | Sweet Pea | Dianthus |
| Aquilegia | Verbena | Marigold |
| Antirrhinum | Viola | Stock |
| Geranium | Centurea | Vinca |
| Ageratum | Larkspur | Zinnia |
| Browallia | Phlox | |
| Nicotiana | Portulaca | |
| Snapdragon | Nemesia | |
| Helichrysim | Nasturtium | |
| Gloxinia | ||
| Gallardia | ||
| Ficus | ||
| Exacum | ||
| Streptocarpus | ||
| Saintpauliu | ||
| Kalanchoe | ||
| Calceolaria | ||
| Gerbera | ||
| Ageratum | ||
| Columbine | ||
| Lobelia | ||
| Platycodon (Balloon Flower) | ||
| Poppies | ||
| Osteospermum (African Daisy) | ||
| Lihtonia |